Black snakes: A beneficial native of the valley

A hand written note was attached to a package our delivery man left. It read, "Just saw big snake on porch."

Doug Pifer

During the 20 years we've lived in the Shenandoah Valley, we've carried on a neighborly relationship with black rat snakes.

Several black rat snakes live in the walls of our house, emerging around the middle of April. They conduct their lives pretty much undisturbed by us, shedding their skins, mating and waiting around to get any tasty young starlings that might be nesting in the walls. We haven't begrudged them their share of young chickens and eggs over the years, nor their occasional forays on nesting birds. They keep away rats and eat mice.

The black rat snake is one of northern Virginia's commonest reptiles. Big adults are usually jet black above, checkered gray and white beneath, and can reach the thickness of a man's wrist. Of course everyone has a snake story, and the bigger the snake the better the story. A record length for a Virginia black rat snake is 6 feet 8 inches. But snakes grow throughout their lives and black rat snakes have been known to live over 20 years, so it's very possible someone has seen a longer snake than that.

A black rat snake is a non-venomous constrictor. This means that it doesn't immobilize its live prey with venom, but instead captures it in its jaws, wraps its powerful body around it and squeezes. Constriction doesn't crush the prey, but simply stops the animal from breathing so the snake can then swallow it when it is immobile and unconscious. This prey may be any bird or small mammal the snake can swallow whole. I once watched a black rat snake swallow one of our hen's eggs whole. Using powerful jaw muscles, the big snake moved the egg down its gullet by alternately moving its jaw bones, which are not fused in front. They're connected only by an elastic muscle that allows the snake to "walk" its loosely connected jaws over the prey. Backward-pointing teeth grip and speed up the process.

After eating a full meal, a snake often rests several days. Strong digestive juices break down feathers, egg shells, bones, hair parts that would be indigestible by many other animals. After a good meal a snake may not eat again for several weeks.

I've watched one of our black rat snakes climb the trunk of our ancient silver maple trees as easily as if it were level ground. Being legless, snakes appear to move by magic. Swift and agile, snakes propel themselves using several methods, often in combination. Perhaps the most common is by lateral undulations of the body. A snake places itself in several loose loops and pushes forward against the irregularities of tree bark, gravel or vegetation. Alternatively, a snake moves by positioning the middle of its body into several S-curves, then extending the head and neck forward to secure another "foothold," then pulling its weight forward, accordion fashion. Finally there's the "tank method." Perhaps you've seen a snake slide smoothly along the ground in a straight line as though on wheels. A snake accomplishes this by using strong muscles to move the skin on its belly forward. Belly scales are very wide and, like plates on a tank track, they catch on the slightest irregularity and pull the snake forward..

Black rate snakes mate soon after they come out of hibernation in spring. They lay their soft-shelled, whitish eggs in sawdust piles, under rotted wood or in similar places where they can be incubated by heat produced by decaying organic material such as in our compost heap. When young black rat snakes hatch later in the summer they are light gray with a pattern of dark splotches. These dark areas fill in gradually as they grow older. Even large, black adults often have white or light-colored skin between the scales.

A snake's flicking tongue unnerves some people, but that's how the snake senses its environment. With its mouth closed a snake thrusts its tongue out through a small notch in the middle of its upper jaw. Forked tips of the extended tongue pick up molecules from any object they brush against or from the air. These forked tips are withdrawn against paired receptacles in the roof of the snake's mouth called the Jacobson's organ. There the molecules are processed and interpreted by the snakes nervous system and brain. A snake thereby can recognize the presence of good, a mate or an enemy.

Times-Courier nature writer Doug Pifer, with a keen eye on the natural world around us, writes from White Post.